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# \_.isUndefined（是否为undefined）

**语法：**

```javascript
_.isUndefined(value)
```

**源代码链接：**[source](https://github.com/lodash/lodash/blob/4.17.10/lodash.js#L12197)

**npm包链接：**[npm package](https://www.npmjs.com/package/lodash.isundefined)

**描述：**

检查`value`是否是`undefined`.

**开始版本：**0.1.0

**参数：**

* `value (*)`: 要检查的值。

**返回值：**

* `(boolean)`: 如果 value 是 undefined ，那么返回 true，否则返回 false。

**例子：**

```javascript
_.isUndefined(void 0);
// => true

_.isUndefined(null);
// => false
```